Their vocal cords — as much as the substance of their words — could influence who becomes the next president, claim the people who study, measure, “focus-group” and coach the human voice.

“Voice matters — it’s what sells,” says John Daly, a University of Texas communications professor who has written a book about persuasion. University of California at Los Angeles psychology professor Albert Mehrabian even claims to have quantified how important a voice is. When we are deciding whether we like the person delivering a message, tone of voice accounts for 38% of our opinion, body language for 55% and the actual words for just 7%, his studies suggest.

Voice analyst Susan Miller talks about four of the candidates’ voices. Listen to the highlights, and short clips of the candidates that were analyzed.
A sortable chart compares the pitch, loudness, speed and variability of the candidates’ voices.

A person’s voice can be a hindrance or a powerful tool. Dr. Miller explains what our voices say about us and how we can help control that message.

To gauge what the candidates’ voices say about their appeal, The Wall Street Journal asked Washington voice coach Susan Miller of VoiceTrainer LLC to analyze the voices of seven Democrats and five Republicans by pitch, speed, and two measures of variability — how loud and soft their voices are, and how high and low they go.

Ms. Miller also toted up the “ums” and “ahs” in two 20-second samples of each candidate’s voice. The samples were taken from a May 7 Republican debate and a July 24 Democratic debate. The samples for former television actor and Tennessee Sen. Fred Thompson were taken from the Sept. 5 speech in which he announced his candidacy.

The vocal-cord primary, like the campaign itself so far, is inconclusive. But our unscientific poll of Ms. Miller and other leading voice experts suggests:

Among the Republicans, former Massachusetts Gov. Mitt Romney’s and television actor Thompson’s baritones win on authority, but lose on energy.

On the Democratic side, New York Sen. Hillary Rodham Clinton’s and Illinois Sen. Barack Obama’s voices convey caring. But Mrs. Clinton can sound shrill and Mr. Obama can lack forcefulness.

Keen to preserve the appearance of authenticity, the presidential campaigns said they aren’t using voice coaches. (Sen. Clinton’s campaign alone didn’t return emails seeking comment). Voice coaches generally won’t say whether they are helping a specific candidate, although none of those commenting in this article are involved in campaigns.

Politics is partly about likability, of course. Ronald Reagan’s voice conveyed warmth and was part of his popularity, says the University of Pennsylvania’s Kathleen Hall Jamieson, who studies political communication. Al Gore’s voice came across as condescending, and hurt him in the 2000 campaign, she says.

Mr. Thompson’s honeyed voice is a big part of his appeal: Supporters compare it with President Reagan’s. But at 121 hertz, a measure of vibrations per second, Mr. Thompson’s voice was higher pitched than that of Republican rival Mr. Romney in the samples, and also showed less variation in pitch and loudness than the voices of most of his other rivals, Ms. Miller calculated.

A high-pitched voice, on the other hand, suggests nervousness, excitability, sometimes even wackiness. Think Ross Perot or Howard Dean, whose scream after his third-place finish in the 2004 Iowa caucuses may have sunk his campaign.

Pitch variability, or inflection, may be almost as important as pitch because it suggests passion and energy. On that measure, Sen. Clinton outdistanced the pack. The difference between her highest- and lowest-pitched words was almost triple the score of Mr. Romney, who had the least inflection.

Mr. Romney also had the least difference between his loudest and softest words — 16 decibels compared with 30 decibels for Sen. Obama, who modulated his volume the most. Those variations in pitch and volume, plus switch-ups in speed, create what UCLA’s Mr. Mehrabian calls “arousal” in an audience. That draws in listeners by creating excitement.

“Emotionally, [voters] will want to embrace your ideas because you have touched them with your passion,” adds Richard Greene, a Los Angeles public-speaking coach.

Those vocal gymnastics convey energy but also require it. Thus Mr. Romney’s near monotone risks reinforcing the fear of party pros that he won’t galvanize voters, says Mr. Greene. Mr. Thompson’s voice, which was only slightly more energetic, plays into his opponents’ attempt to cast him as a lazy campaigner, Mr. Greene adds.

But the pitch variability in Mrs. Clinton’s Midwestern dialect may not be entirely good news if it comes across to voters as shrieking rather than passion. Mrs. Clinton’s pitch is within normal range for a woman, says Ms. Miller. Yet her sudden vocal highs run the danger of making her sound strident, says the University of Pennsylvania’s Ms. Jamieson.

Mr. Obama has mastered the moving cadence used by many black clergymen to rouse his audiences, speech coaches say. But the Illinois senator punctuated his answer with six “uhs,” which voice researchers call “disfluencies.” A candidate with too many disfluencies sounds unprepared; a candidate with too few can sound rote and unreflective.

Sen. Clinton, who is often criticized as over-rehearsed, blitzed through a question about nuclear energy at 207 words per minute without a disfluency. But she slowed and uh’ed when asked whether she is a liberal.

Mr. Daly says research shows that people who speak a bit faster than normal are perceived as more competent, persuasive, even likable — if only because they don’t allow listeners time to think about what they’ve just heard. The average English speaker utters 125 to 150 words a minute and comprehends about twice that, he says.

By that measure, Mr. Kucinich was speaking at the outer edge of human comprehension in one sample, at 273 words per minute. Even Mr. Thompson’s Southern drawl clocked in at 207 words a minute on one sample.

Speech slows with age and loses clarity, which some voice professionals say could be a problem for 71-year-old Arizona Sen. John McCain. Mark McKinnon, a McCain campaign adviser, calls the senator’s voice “gritty.” But Frank Luntz, a Republican pollster who has written about how words influence public debate, says he hears age in Mr. McCain’s voice.

Of course, none of this may matter if voters have other reasons to like or dislike a candidate. That certainly happened with Mr. Giuliani’s lisp. “It should have hurt him and it doesn’t, and no one’s going to make fun of him for it after 9/11,” says Mr. Luntz.

Voters also are quick to change their minds as momentum builds behind a candidate. George H. W. Bush’s high-pitched voice aggravated the “wimp factor” in his 1988 presidential campaign but wasn’t an issue after he was elected, says Ms. Jamieson.

So what would a Clinton-Giuliani match-up sound like, if opinion polls are correct when they predict the two will lead their parties’ tickets?

Mr. Giuliani gets points for lower pitch and its implication of authority. Mrs. Clinton wins on inflection, with its suggestion of deep concern. And on speed, both give new definition to a New York minute.